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Definitions

• the invention relates generally to the field of molecular medicine.
• the invention pertains to methods and compositions for modulating the function of transcription factors, especially transcription factors that recruit epigenetic regulators (hi stone modifying enzymes) to specific DNA promoters.
• the targeted transcription factors include but are not limited to the myocyte enhancing factor (MEF2), the forkhead/winged helix transcription factor FOXP3 and the transcription factor GATA3.
• MEF2 myocyte enhancing factor
• FOXP3 forkhead/winged helix transcription factor
• GATA3 transcription factor
• the invention pertains to small molecule modulators of MEF2 and its associated factors that include but not limited to histone deacetylases (HDACs), p300/CBP and Cabinl and the therapeutic applications thereof.
• HDACs histone deacetylases
• This invention relates to the use of small molecules for modulating the functions of transcription factors that are associated with certain diseases.
• Transcription factors are proteins that bind to specific DNA sequences and regulate gene expression either directly or through associated proteins such as co-activators and co-repressors, or by recruiting histone modifying enzymes such as histone acetyltransferases (HATs) and histone deacetylases (HDACs).
• HATs histone acetyltransferases
• HDACs histone deacetylases
• the other is to develop small molecules to block the recruitment of HAT (such as p300 and CBP) and HDACs and other histone modifying enzymes (such as histone methyltransferases, and demethylases, DNA methyltransferases ) and chromatin remodeling machineries to specific regions of chromatin.
• this invention relates to the myocyte enhancer factor-2
• MEF2 has been implicated as a key regulator of hypertrophic responses in heart muscle cells. Heart hypertrophy induced by pathological stimuli can lead to heart failure in many forms of cardiovascular diseases.
• MEF2 generally defines a family of transcription factors with four members: MEF2A, MEF2B, MEF2C and MEF2D. The importance of their function has been demonstrated in detail through the use of murine and Drosophila genetics (Potthoff and Olson, 2007). MEF2, in skeletal muscles where it was initially identified, together with myogenic basic helix-loop-helix transcription factors such as MyoD, promotes and maintains myogenesis
• MEF2A one member of the MEF2 family
• CAD coronary artery disease
• MI myocardial infarction
• MEF2 is now known to be a general transcriptional factor in many other cell types.
• MEF2 is one of the important transcriptional factors for mediating calcium signaling in lymph system development ⁇ (Pan et al., 2004; Youn and Liu, 2000; Youn et al., 1999).
• MEF2 regulates cytokine expression and immune responses.
• MEF2 also regulates transcription programs underlying neuronal survival and synaptic remodeling (Chen and Cepko, 2009; Flavell et al., 2006; Flavell and Greenberg, 2008; Flavell et al. s
• MEF2 Inside cells, the action of MEF2 includes three distinct steps: (i) transcriptional repression; (ii) calcium-dependent de-repression; and (iii) transcription activation. Transcriptional repression by MEF2 depends on its association with a variety of transcriptional co-repressors with intrinsic or associated histone deacetylase (HDAC) activity. In T cells, MEF2 bind Cabin I, which in turn associate with class I HDACs such as HDACl, HADC2 and HDAC3 (Youn and Liu, 2000).
• HDAC histone deacetylase
• MEF2 binds directly to class II HDACs such as HDAC4, HDAC5, and HDAC9 and inhibits the expression of specific genes involved in the development and adaptive responses of muscle (Chan et al., 2003; Gregoire et al., 2006; Gregoire and Yang, 2005; McKinsey et al., 2001, 2002; Miska et al., 1999; Sparrow et al., 1999).
• Mice whose HDAC5 or HDAC9 has been knocked out showed increased sensitivity to hypertrophic stimuli, suggesting important roles of class II HDACs in heart hypertrophy (Potthoff and Olson, 2007).
• HDACs histone deacetylases
• HDAC5 and HDAC9 are key mediators of hypertrophic signals in cardiomyocytes.
• MEF2/class II HDAC pathway is potential therapeutic target for heart hypertrophy.
• MEF2 In response to specific calcium signals, Cabin 1 and HDACs are removed from MEF2 (Potthoff and Olson, 2007). MEF2 then recruits co-activators such as p300 and CBP to turn on distinct programs by association with a variety of transcriptional activators and co-activators (McKinsey et al., 2001; Sartorelli et al., 1997; Slepak et al., 2001; Wei et al., 2008). A small increase of p300 has been shown to be necessary and sufficient to induce MEF2- dependent cardiac hypertrophy. MEF2 has a highly conserved N-terminal region (residues 2-93), consisting of the well-characterized MADS-box and a
• MEF2-specific domain (Shore and Sharrocks, 1995).
• the MADS-box/MEF2 domain is remarkably rich in function, mediating DNA binding, dimerization, and protein-protein interactions with a myriad of MEF2 transcription partners (McKinsey et al., 2001, 2002), including Cabinl, Class Ha HDACs and p300/CBP. It has been shown that the MADS-box/MEF2 domain in MEF2 is necessary and sufficient to bind with a small motif conserved in class II HDACs and Cabinl.
• the CH3 domain of p300 and CBP is also shown to bind the MADS-box/MEF2 domain.
• MEF2 is a relatively small transcription factor without any apparent enzymatic activity; its main function is to bind specific DNA and recruit transcription co-regulators such as Cabinl, class II HDACs and p300/CBP to specific promoters. This mode of function is generally considered not druggable or at least very difficult to target by small molecules.
• MEF2-associated diseases including inflammation, autoimmune diseases, neurodegenerative diseases, cancer, and cardiovascular disease.
• FOXP3 forkhead/winged helix transcription factor
• FOXP3 is a key transcription factor critical to the development and function of regulator T cells (Tregs).
• Tregs are a special population of T cells required for suppressing the excessive activation of the immune system.
• Elevated FOXP3 function can be beneficial in treating autoimmune diseases and transplant rejection while strategic down regulation of FOXP3 activity can be used to develop immune- based anti-tumor therapies (Zuo et al,, 2007a; Zuo et al., 2007b).
• small molecules that bind FOXP3 and modulate its interaction with co-repressors and co-activators could have therapeutic application in autoimmune diseases, transplant rejection and cancer therapy.
• FOXP3 Similarly to MEF2, the function of FOXP3 is tightly regulated by transcription co-regulators that include HAT (such as TIP60) and HDACs (including class I and class II HDACs) (Li et al., 2007).
• HAT such as TIP60
• HDACs including class I and class II HDACs
• small molecules could be developed by methods described in this invention that binds FOXP3 and blocks its interaction with co-regulators including epigenetic regulators such as histone modifying enzymes and chromatin remodeling machines.
• Histone deacetylases (EC number 3.5.1) are a class of enzymes that remove acetyl groups from an ⁇ -N-acetyl lysine amino acid on a histone. Its action is opposite to that of histone acetyltransferases (HATs).
• HDACs proteins are now also being referred to as lysine deacetylases (KDAC) to more precisely describe their activity rather than their target, which also includes numerous non-histone proteins.
• KDAC lysine deacetylases
• Histone proteins are the chief protein components of chromatin. They act as spools around which DNA winds and play an important role in gene regulation and DNA packaging. Histone proteins have tails that are normally positively charged due to the amine groups present on their lysine and arginine amino acids. These positive charges help the histone tails to interact with and bind to the negatively charged phosphate groups on the DNA backbone.
• HATs facilitate histone acetylation and are thus believed to be transcriptional activators.
• HDACs serve to remove acetyl groups from histones and thereby repress transcription.
• HDACs alter global gene transcription through the deacetylation of chromatin. It should be noted that HDACs do not directly bind DNA sequence and require additional factors for target gene recognition (Morrison et al., 2007).
• HDAC proteins There are 4 recognized subtypes of HDAC proteins (class I - IV) based on function and DNA sequence similarities. The first two subtypes are considered "classical" HDACs whose activity are inhibited by trichostatin A (TSA). Class I HDACs includes HDACs 1, 2, 3 and 8, which are expressed ubiquitously (Zhang and Olsen, 2000). Class II HDACs has two subgroups, Ha that includes 4, 5, 7 and 9, and lib that includes HDAC6 and HDAClO. Class Ha share a common structural organization, with carboxyl-terminal catalytic domain and an amino-terminal extension that mediates interactions with members of the myocyte enhancer factor 2 (MEF2) family of transcription factors.
• MEF2 myocyte enhancer factor 2
• HDACs also differ in terms of their subcellular localization with class I generally found in the nucleus, class lib are located mostly in the cytoplasm, while class IIa shuttle between the nucleus and the cytoplasm.
• class I HDACs class Ha HDACs are tissue-restricted, with especially high levels of expression in heart, skeletal muscle, and brain (Zhang et al., 2002).
• Class III is a family of NAD + -dependent proteins not affected by TSA and class IV is considered an atypical category of its own.
• HDACl 1 is grouped in class V. Given the important roles that HDACs play in cellular processes, the medical applications of HDAC inhibitors (HDACi) is an intense area of research.
• HDACi HDACi-oxide-semiconductor
• valproic acid as mood stabilizers and anti-epileptics.
• the anticonvulsant property of valproic acid was accidentally discovered when it was being used as a vehicle for a number of other compounds that were being investigated as anticonvulsant. It was not until later that valproic acid was identified as a HDACi.
• HDACi are being actively studied as a mitigator or treatment for neurodegenerative diseases. There has also been extensive effort to develop HDACi for cancer therapy.
• Vorinostat has recently been approved for treatment of cutaneous T-cell lymphoma (CTCL).
• CTCL cutaneous T-cell lymphoma
• FK228 cyclic depsipeptide natural product FK228
• HDACs HDACs.
• valproic acid a clinical trial is studying the effects of valproic acid on the latent pools of HIV in infected persons.
• HDACi the exact mechanisms by which these compounds work are still not well understood.
• these efforts are largely guided by guesswork and trial-and-error experiments.
• HDACi One particular problem with the use of HDACi is that most of the known small molecules that inhibit HDAC activity are designed to function by targeting the catalytic activity of HDACs. However, since the active site is a conserved feature shared by a large number of different HDAC isoforms, it is inherently difficult to identify isoform-selective HDACi. Therefore, most HDACi have low specificity and are incapable of specific targeting of any particular species of HDAC.
• TSA trichostatin A
• HDAC trichostatin A
• HDACi have the general structure R-L-Z, where R is a protein surface recognition group connected via a short fatty linker L to a Zn 2+ -chelating group Z that binds to the active site zinc atom.
• R is a protein surface recognition group connected via a short fatty linker L to a Zn 2+ -chelating group Z that binds to the active site zinc atom.
• Z chelating groups
• TSA vorinostat
• LAQ824 belinostat
• FK228, largazole thiol derivatives
• electrophilic ketones trapoxin A
• HDACi Another class of known HDACi are the benzamides that feature an ortho-aminoani ⁇ ide (2-aminoanilide) moiety, including MS-725, MGCD0103, pimeloylanilide ortho-aminoanilide (PAOA) and compound 106 (N'-(2- aminophenyI)-N 7 -/>-tolylheptanediamide) which was investigated as a potential therapeutic for neurodegenerative diseases including Friedreich's ataxia and Huntington disease (Chou et al., 2008; Herman et al., 2006; Paris et al., 2008; Rai et al., 2008; Thomas et al., 2008; Wong et al., 2003).
• HDACi Several additional factors resulting from the well-regulated biological roles of the various HDAC isoforms, impose further challenges for the conventional approaches to the design of HDACi.
• Experiments have shown that the amount of acetylated histones increases in the presence of HDACi.
• recruitment of HATs and HDACs by DNA-bound transcription factors results in the formation of multi-protein transcription regulatory complexes that confer cell type specificity and signal dependent regulation to arrays of subordinate genes.
• HDACi that inhibit HDACs indiscriminately is akin to throwing a monkey ranch into a complicated and delicately balanced machine. This explains the numerous undesirable side-effects observed in many of the trials involving HDACi.
• Epigenetic regulation is the establishment of inheritable gene expression patterns without permanently changing the DNA sequence. It has emerged as a key mechanism for regulating cellular function.
• Alteration of epigenetic regulation is a hallmark of many diseases, especially cancer. Small molecules that are being developed as drugs in treating these diseases, typically found via phenotypic screening, act by modulating the epigenetic control of cellular process. As such, the fundamental mechanisms of epigenetic regulation is an area of intense interest.
• HDACs' role in regulating DNA transcription can be viewed as a component of epigenetic regulation. Similar to HDACi, the majority of current chemical modulators of epigenetic regulators inhibit these enzymes by binding to their catalytic site, which is often shared by multiple enzymes with distinct cellular roles.
• MEF2 transcription factors
• this invention also provides methods for identifying, screening, assaying, and synthesizing small molecule modulators that are capable of binding to a site lying in the interfacial surface of the factor-cofactor complex, thereby, disrupting the formation of the complex.
• this invention has solved the long standing problem of targeting the heretofore "undrugable” transcription factors such as MEF2.
• this invention provides an alternative approach for the development of small molecule modulators of HDAC function. Rather than targeting the active site of a particular HDAC, the present invention targets the binding site of the HDAC with an associated transcription factor which is required for regulating transcription. Because different HDAC subtype will have different binding surface to different transcription factor, by targeting the interface of these protein-protein interactions, the specificity issue posed by the conservative active site is resolved. [0032] In particular, the present invention targets the interaction between the transcription factor MEF2 and class Ha HDACs. The activity of MEF2 is controlled by class Ha HDACs that bind MEF2 on specific promoters to repress target gene expression (Potthoff and Olson, 2007).
• HDACi small molecule inhibitors of HDACs
• Class I ⁇ a HDACs function closely with MEF2 in muscle, neurons and T cells.
• Class Ha HDACs do not bind DNA but depend on its interaction with DNA-bound MEF2 for promoter targeting. This interaction is mediated by a short amphipathic helix conserved in class Ha HDACs but not other HDACs that binds to a hydrophobic groove on the MADS-box/MEF2 domain of
• MEF2 (Guo et al., 2007; Han et al., 2005; Han et al, 2003).
• Such a ligand/receptor like binding mechanism suggests that it might be possible to use small molecules to block the recruitment of class Ha HDACs to MEF2- specific promoters (Guo et al., 2007; Han et al., 2005; Han et al., 2003).
• the invention is based on systematic structure and biochemical studies
• small molecules binding to MEF2 can modulate its activity in the recruitment of transcription co-regulator such as Cabinl, class Ha HADCS and p300/CBP.
• transcription co-regulator such as Cabinl, class Ha HADCS and p300/CBP.
• Most of the these co-regulators have intrinsic function to modify chromatin (e.g. HDACs, p300 and CBP) or the ability to recruit chromatin modifying enzymes and machinery (e.g. mSin3A that binds Cabinl, HPl, CtBP, 14-3-3 that binds class Ha HDACs ).
• chromatin modifying enzymes and machinery e.g. mSin3A that binds Cabinl, HPl, CtBP, 14-3-3 that binds class Ha HDACs .
• small molecules that bind MEF2 and modulate its interactions with other transcription co-regulators can serve as epigenetic modulators in tissues where MEF2 play key regulatory roles. These small molecules can
• MEF2-dependent gene expression is dysregulated.
• the dysregulation could result from genetic mutations of MEF2 and its associated factors, diminished or excessive signals leading to the reduced or overly activated MEF2 function, abnormal under- or over-expression of co-factors that bind and interact with MEF2.
• Potential clinical applications of the MEF2-binding small molecules include but not limited to diseases from the muscle, immune and nervous systems. In the muscle system are cardiac hypertrophy, muscle fiber type remodeling, and other muscle related diseases resulting from imbalanced MEF2 function. In the immune system are a variety of autoimmune diseases or immune deficiency that result from excessive or too little MEF2-dependent gene expression.
• MEF2-binding small molecules can also be used to manipulate the function of regulatory T cells and the overall immune response for preventing transplant rejection.
• MEF2-dependent gene expression is intimately linked to synapses remodeling and neuronal survival
• MEF2- binding small molecules can also be used treat a variety of neurodegenerative diseases (e.g. Alzheimer's disease and Huntington disease etc), autism, psychiatric disorders, and impaired learning and memory that result from deregulated MEF2 function.
• small molecule modulators of this invention operate by targeting binding sites located at the protein-protein interaction interface of the transcription factors and their co-factors, they are also referred to herein as interfacial inhibitors.
• the invention provides an assay for screening, identifying, or optimizing a candidate interfacial inhibitor.
• Assays in accordance with this aspect of the invention will generally include the steps of contacting the candidate interfacial inhibitor to an evaluating element comprising a molecular surface defined by a protein-protein interface, which includes beta strands Sl, S2 and S3 and helix H2 of each MEF2 monomer and the short helix motif from Cabin 1 and HDAC4 and FIDAC 9.
• the evaluating element is operatively coupled with a reporting element that provides information about the candidate inhibitor.
• the assay is a cell-based Iuciferase assay that allow rapid and high throughput screen and optimization of small molecules that bind MEF2 and modulate its binding to transcription co-regulators.
• This assay is developed based on more than 10 years of structural and biochemical studies of MEF2 complexes by the inventor's laboratory. This invention claims that the protein-protein interface, first identified by crystallography studies, and further demonstrated by structure-guided mutation studies in the invention, could serve as the molecular basis for a highly specific and sensitive screen for MEF2-binding small molecules.
• the evaluating element of the assay may be implemented with physical assays that include but are not limited to pull down, coimmunoprecipitation or fluorescence quenching and anisotropy or any in vitro binding assays and cell- based luciferase reporter assay, transgenic reporter assay that are based on the protein-protein interface indentified by this invention.
• this invention also provides compounds useful as epigenetic modulators of MEF2-dependent transcription in a variety of mammalian tissues that include but are not limited to muscle, immune and nervous systems.
• compounds in accordance with this aspect of the invention may include but are not limited to the previously published compounds (Chou et al., 2008; Herman et al., 2006; Paris et al., 2008; Rai et al., 2008; Thomas et al., 2008; Wong et al., 2003), pimeloylanilide orthoaminoanilide PAOA, and the commercially available homolog suberoylanilide orthoaminoanilide, or BML-210, as well as their structurally related derivatives.
• this invention also provides a molecular framework defined by the BML-210 binding site on MEF2 derived from the structural frame work established by the crystal structure of BML-210 bound to MEF2, as set forth in the crystal structure coordinates in Table 1.
• BML-210 adopts an extended conformation to bind into the hydrophobic pocket of the MEF2 ( Figure 1d).
• One end of the molecule, the phenylamide group is surrounded by a number of hydrophobic residues including Leu66, Leu67, Thr70, Leu66' (prime sign denote residues from the other monomer) and Thr70'.
• the amide group at this end is also in position to engage in hydrogen bonding interactions with Thr70 and Thr70', respectively.
• the ring-link electron density is in a more hydrophilic environment surrounded by Asn73, Gln56 ! , Asp61' and Asp63'.
• This region correspond to the ortho-aminoanilide group.
• the ortho- aminoanilide moiety with its amide group make extensive van der waals contacts and potential hydrogen bonding interactions with residues of MEF2 (Figure Id)
• the methylene groups of the octanediamide fit snugly between helix H2 of the two MEF2 molecules, making numerous contacts to the main chain and side chain of MEF2 residues, mostly of hydrophobic nature (Figure Id).
• the crystal structure of BML-210 bound to MEF2 disclosed in this invention in addition to defining the small molecule MEF2- binding site as described herein, it also reveals for the first time a likely binding site for the ortho-aminoanilide moiety present in BML-210 and in other benzamide-containing HDAC inhibitors. Notably, this binding site is different from the HDAC enzyme's active site as has been postulated previously for this class of HDAC inhibitors.
• the invention provides MEF2-binding small molecules useful for binding to the interfacial binding site defined by the molecular framework in the third aspect above.
• the provided molecules are MEF2-binding small molecules with a general structural formula derived from the identified binding site derived from the crystal structure of BML-210 bound to MEF2.
• the provided small molecules are designed to bind to the described structural fold and would potentially bind
• the compounds provided under this embodiment of the invention include compounds of the general formula R a -L- R b that bind to the MEF2 binding site, wherein:
• R c and R d are independently selected from a group consisting of hydrogen, alkyl, alkenyl, alkynyl, alkoxy, aryl, heteroaryl, alkylamino, dialkylamino, arylamino or heteroarylamino.
• L is a linker consisting of a chain of up to 20 carbon atoms, provided that up to three carbon atoms can be replaced with an oxygen, nitrogen or sulfur atom, and further provided that it can include substituents selected from a group consisting of: alkyl, alkenyl, alkynyl, aryl, heteroaryl, benzo, hydroxy, alkoxy, aryloxy, oxa, keto, amido, sulfonamido, or fluoro
• R c and R d are independently selected from a group consisting of hydrogen, alkyl, alkenyl, alkynyl, alkoxy, aryl, heteroaryl, alkylamino, dialkylamino, arylamino or heteroarylamino.
• the provided compounds have the general structure Ar 1 -L 1 -L 2 -L 3 -Ar 2 wherein:
• Ar 1 and Ar 2 are aromatic rings independently selected from a group consisting of benzene, naphthalene, pyridine, pyrimidine, pyrazine, quinoline, isoquinoline, pyrrole, furan, thiophene, imidazole, pyrazole, oxazole, thiazole, isoxazole, indole, benzimidazole, benzothiazole, benzoxazole, provided that the aromatic ring may contain up to seven substituents selected from a group consisting of: hydrogen, alkyl, alkenyl, alkynyl, alkoxy, aryl, heteroaryl, amino, alkylamino, dialkylamino, arylamino, heteroarylamino, hydroxy, or halo. The substituents can also join together to form a ring of up to 12 atoms,
• L 2 is a linking group selected from a group consisting of a chain of up to
• R 1 - R 10 are independently selected from a group consisting of
• L 2 is a linking group selected from a group consisting of a chain of up to 10 carbon atoms, provided that up to three atoms can be replaced with an oxygen, nitrogen or sulfur atom, and further provided that these atoms can contain substituents selected from a group consisting of: alkyl, alkenyl, alkynyl, aryl, heteroaryl, benzo, hydroxy, alkoxy, aryloxy, oxa, keto, amido, sulfonamido, or fluoro
• the provided compounds are selected from the following list of compounds (Fig. 2)
• the invention also provides compounds and compositions useful for treating diseases that result from deregulation of MEF2-dependent transcription.
• Compositions in accordance with this aspect of the invention will include one or more of a compound capable of blocking binding of MEF2 and its co-factors.
• the provided compounds and compositions can be used in therapeutic applications involving the modulation of epigenetic regulation associated with the interaction of transcription factors and their recruited histone-modifying enzymes.
• the provided MEF2-binding small molecules can be used to treat a variety of diseases resulting from deregulation of MEF2-dependent transcription, which include but not limited to cardiac hypertrophy, muscle fiber type remodeling, and other muscle-related diseases resulting from imbalanced MEF2 function; autoimmune diseases or immune deficiency that result from excessive or too little MEF2-dependent gene expression, and transplant rejection; a variety of neurodegenerative diseases (e.g. Alzheimer's disease and Huntington disease etc), autism, psychiatric disorders, and impaired learning and memory that result from deregulated MEF2 function.
• a further application of this embodiment of the invention involves small molecules that modulate the function of the FOXP3 transcription factor that can be used to treat a variety of diseases that result from deregulation of FOXP3 -dependent transcription.
• These diseases include but not limited to autoimmune diseases, transplant rejection and cancer.
• the sixth embodiment of this invention involves the preparation of the drug:MEF2 complex and its crystallization for structure determination.
• This protocol define the specific protein fragment of MEF2A (2-78) and the range of buffer conditions to obtain high quality of crystals of compounds bound to MEF2.
• This method of complex preparation and crystallization is essential for structural characterization of current and future small molecules bound to MEF2 and use the structure to guide the optimization of the lead compounds.
• Figure 1 shows three different depictions (a-c) of a crystal structure of
• MEF2 and the identified ligand binding site (d) shown is BML-210 bound to MEF2A (1-78) at 2.4 A resolution, including the amino acids involved in binding interactions with BML-210.
• Figure 2 shows the structures of BML-210, PAOA and related exemplary MEF2-binding molecules.
• FIG. 3 shows a schematic diagram of MEF2-HDAC luciferase reporter assay for FfDACi.
• Figure 4 shows normalized response for luciferase activity in MEF2-
• HDAC luciferase reporter assay 24 hrs after treatment with BML-210.
• the luciferase activity decreased in a dose dependent manner.
• Figure 5 shows competitive inhibition of MEF2 binding to HDAC after incubation with BML-210 in Biacore assay; (b) Structural analysis showing that BML-210 and HDAC9 bind overlap regions on MEF2.
• HDACs HDACs
• a small subset or even a specific member e.g. cancer therapy
• others e.g. neurodegeneration and inflammation
• inhibitors of class I and class II HDACs can be grouped into six categories based on the key features of their chemical structures: (1) hydroxamic acids; (2) thiol-containing molecules; (3) electrophilic ketones; (4) short-chain fatty acids; (5) benzamides (ortho- aminoanilides); and (6) cyclic depsipeptides.
• HDAC inhibitors have shown different activities on different classes of HDACs.
• members of the hydroxamic acids category such as TSA and SAHA
• PAOA pimeloylanilide ortho- aminoanilide
• MS-275 MS-275
• CI-994 CI-994
• MGCD-0103 cyclic peptide family
• HDACs often exist in large multi-protein complexes with specific co-regulators and other chromatin modifying enzymes
• a mechanism-based approach may offer a better pathway to identifying and optimizing novel HDAC-based small molecule epigenetic regulators. That is, instead of targeting the active site of the enzyme as dictated by conventional approaches of drug design, one would develop small-molecules targeting the protein-protein interactions between HDACs and their relevant functional partners.
• this invention provides a method of modulating HDAC function by blocking the binding of HDAC to an associated transcription factor.
• methods according to this aspect of the invention will have the steps of: contacting the transcription factor with interfacial inhibitor, wherein the interfacial inhibitor is capable of selectively binding to a site within the interfacial surface between the transcription factor and HDAC, thereby preventing this HDAC from performing its catalytic activity at protein sites that are located in the vicinity of the DNA-binding site of the transcription factor.
• the HDAC may be any HDAC isoform from a classical HDAC or a subset thereof.
• Exemplary HDAC may include HDAC 4, 5, 6, 7, 9 and 10, or any subset thereof.
• the HDAC is a class Ha
• HDACs and in a further preferred embodiment the HDAC is either HDAC4 or HDAC9.
• the transcription factor may be any transcription factor known to bind to the HDAC.
• Exemplary transcription factors may include MEF2, FOXP3, GATA3, and Cabinl but are not limited thereto.
• the transcription factor is MEF2.
• the interfacial inhibitor may be a small molecule.
• Methods described herein above may be used in a research setting for obtaining information regarding the function and mechanisms of a HDACs and the counterpart transcription factor in vivo or in vitro. They may also be used in a clinical setting for treating diseases.
• Diseases that may be treated with methods of this invention are generally those involving cardiac hypertrophy, muscle fiber type remodeling, and other muscle-related diseases resulting from imbalanced MEF2 function; autoimmune diseases or immune deficiency that result from excessive or too little MEF2-dependent gene expression, and transplant rejection; a variety of neurodegenerative diseases (e.g. Friedrich's ataxia, Alzheimer's disease and Huntington disease etc), autism, psychiatric disorders, and impaired learning and memory that result from deregulated MEF2 function.
• Exemplary diseases may include neurodegenerative diseases, heart diseases, autoimmune diseases, inflammation, and cancer, but are not limited thereto.
• methods in accordance with this aspect of the invention will include the general steps of: administering to a patient a pharmaceutically effective amount of a blocking agent, in which the blocking agent is capable of blocking the binding of a HDAC to a transcription factor.
• methods in accordance with this aspect of the invention will include the general steps of: administering to a patient a pharmaceutically effective amount of a blocking agent, in which the blocking agent is capable of blocking the binding of a Cabinl to MEF2.
• Cabinl is a transcription co-repressor of calcineurin-dependent transcription program. It is highly expressed in T cells and neuronal cells.
• methods in accordance with this aspect of the invention will include the general steps of: administering to a patient a pharmaceutically effective amount of a blocking agent, in which the blocking agent is capable of blocking the binding of a p300 to MEF2.
• methods in accordance with this aspect of the invention will include the general steps of: administering to a patient a pharmaceutically effective amount of a blocking agent, in which the blocking agent is capable of blocking the binding of a CBP to MEF2.
• methods in accordance with this aspect of the invention will include the general steps of: administering to a patient a pharmaceutically effective amount of a blocking agent, in which the blocking agent is capable of blocking the binding of any transcription co-regulators that bind MEF2.
• the HDAC may be any classical HDAC or a subset thereof.
• the blocking agent may be a small molecule, a helical peptidomimetic, or a combination thereof, so long as the blocking agent is capable of selectively binding to a site located on the interfacial surface between the HDAC and the transcription factor.
• the transcription factor is MEF2.
• this invention also provides an assay for identifying an interfacial inhibitor capable of binding to an interfacial site between HDAC and a transcription factor so as to block the interactions thereof.
• Assays in accordance with this aspect of the invention will generally have the steps of introducing a test compound to an evaluation element, wherein said evaluation element comprises an interfacial binding site on a
• MEF2 dimer defined by the interface between a first group of structural elements on the MEF2 dimer and a second group of structural elements.
• the first group of structural elements include the beta strands Sl, S2, S3, and the helix H2 of each of the MEF2 monomer (The secondary structural elements and corresponding residue ranges are as described in Han et al,, Nature 2003).
• a two-hybrid system based assay includes a binding domain fused with a bait, an activating domain fused with a prey, and a reporter gene; and determining a reporter signal level.
• the binding domain comprises a MEF2D fused with GAL4 DNA (GAL4-MEF2); the activating domain comprises MEF2 binding motif of HDAC4 fused with VP-16 (HDAC4-VP16).
• the reporter gene is a GAL4- driven reporter plasmid (GAL4Luc), all hosted in a cell host.
• This preferred embodiment of this invention is a cell-based luciferase assay that allows rapid and high throughput screening and optimization of small molecules that bind to a transcription factor such as MEF2 and modulate its binding to transcription co-regulators.
• the assay is developed based on more than 10 years of structural and biochemical studies of MEF2 complexes by the inventor's laboratory.
• This exemplary embodiment based that the protein-protein interface, first identified by crystallography studies, and further demonstrated by structure-guided mutation studies in the invention, could serve as the molecular basis for a highly specific and sensitive screen for MEF2-bi tiding small molecules.
• any assay that based on this protein-protein interface which include beta strands Sl, S 2 and S3 and helix H2 of each MEF2 monomer and the short helix motif from Cabin 1 and HDAC4 and HDAC 9 are considered to be within the scope of this invention
• Other exemplary assay implementations may include any physical assay techniques such as, but not limited to, pulldown, co-immunoprecipitation; fluorescence-based binding assays and functional assays including, but not limited to, luciferase reporter assay, and transgenic reporter assay that are based on the protein-protein interface indentified by this invention.
• HDAC4 plasmid construct is transiently transfected into HeIa Cells. HDAC4 occupation on MEF2 mediated promoters are detected by ChIP using appropriate specific antibodies and PCR primers in the presence of the tested compound and buffer control. A fluorescence imaging based method as an alternative approach to ChIP analysis can also be used. GFP-fused MEF2C and HDAC4 is transfected into HeLa or C2C12 cells to study their interaction.
• GFP-HDAC4 When expressed alone, GFP-HDAC4 localizes in the cytoplasm in a diffusive manner, whereas GFP-MEF2 localizes in the nucleus, also in a diffusive pattern.
• HDAC4 and MEF2 When co-expressed, HDAC4 and MEF2 form punctate bodies inside the nucleus. Although the nature of these punctate nuclear bodies is unknown, their formation is apparently dependent on MEF2:HDAC4 interaction, as a HDAC4 mutant lacking a functional MEF2-binding motif fails to target MEF2 to nuclear bodies.
• MEF2 target genes can further facilitate this method, by selecting well-known MEF2 target genes that show large responses to MEF2-dependent repression or activation in the resting or activated (e.g. with calcium signal turned on) state.
• MEF2 target genes that show large responses to MEF2-dependent repression or activation in the resting or activated (e.g. with calcium signal turned on) state.
• MEF2 co-repressors e.g. Cabinl
• detecting the promoter presence of class Ha HDAC using ChIP and by monitoring expression changes upon drug treatment or after siRNA knockdown of HDAC4, 5, 7 or 9 (expression changes due to siRNA are evaluated first).
• This method can be used to evaluate a compound at a genome-wide level by analyzing gene expression using microarray and by detecting genome-wide binding of class Ha HDACs in the presence of various concentrations of the provided compound.
• this invention also provides a high throughput, highly sensitive and specific screen platform for searching MEF2- binding small molecules.
• This platform comprises stably transformed cell lines containing the GAL4-driven reporter plasm id (GAL4Luc), MEF2D fused with GAL4 DNA-binding domain (GAL4-MEF2), the MEF2-binding motif of GAL4-driven reporter plasm id (GAL4Luc), MEF2D fused with GAL4 DNA-binding domain (GAL4-MEF2), the MEF2-binding motif of
• HDAC4 fused with VP- 16 HDAC4-VPI6
• GAL4 DNA-binding domain fused with VP- 16 positive control
• various compounds as negative and positive controls.
• a kit consistent of the above stable cell lines, plasmids, and control compounds can be made for the screen by users searching for new MEF2-binding molecules and for optimizing existing leading compounds.
• MEF2D By switching MEF2D to MEF2A, MEF2B and MEF2C, one can also use this method to search for compounds that bind selectively to an isoform of the MEF2 family.
• Such compounds can be used to study the function and involvement of specific MEF2 family members in diseases and can be employed in the development of diagnostic agents and for the identification of more specific therapeutic agents for MEF2-associated diseases.
• the invention also provides a method for identifying a subtype-specific HDAC inhibitor/modulator by targeting their regulatory and functional complexes.
• Methods in accordance with this aspect of the invention generally includes the steps of: (1) solving the structure or substructure that contains functionally important interfaces; (2) applying docking analysis to the solved structures by computationally docking test molecules selected from existing or new potential HDAC inhibitors; (3) developing an assay for screening compounds that can disrupt the protein- protein interactions between the HDAC complex of interest; (4) characterizing the compound identified in step (3); (5) optimizing the compound computationally; and (6) synthesizing the optimized compound and validating the compound using the assay of step (3).
• step 1 the structure can be solved by molecular replacement using existing structure as the search model. If necessary, experimental phases can be obtained MAD or MIR.
• step 2 docking can be performed using standard package such as AutoDock.
• Step 3 is as described above and will most be based on mammalian two-hybrid assay. The rest of the steps will depend on the nature of the compounds using methods known in the art.
• the invention also provides compounds useful as blocking agents for blocking the binding between a HDAC and a transcription factor.
• the HDAC may be any classical HDAC or a subset thereof.
• the transcription factor may be any transcription factor known to bind to HDAC, including but not limited to MEF2, FOXP3 and GATA3.
• the transcription factor is MEF2.
• Compounds according to this aspect of the invention include small organic molecules and helical peptidomimetics
• MEF2-binding small molecules can be identified using the method provided herein, by utilizing the disclosed MEF2 binding site as a guide.
• the provided small molecules have a general structural formula derived from the identified binding site revealed from the crystal structure of BML-210 bound to MEF2.
• the provided small molecules are designed to bind to the described structural fold and would potentially bind MEF2 with high affinity and selectivity.
• methods known in the art can be utilized, including but not limited to: computer-aided structure-based design combined with in-silico screening, combinatorial library design combined with high-throughput screening, and fragment-based drug discovery for lead identification followed by lead optimization.
• the compounds provided under this invention include compounds that bind to the MEF2 binding site with the general formula:
• R c and R d are independently selected from a group consisting of hydrogen, alkyl, alkenyl, alkynyl, alkoxy, aryl, heteroaryl, alky lam ino, dialkylamino, arylamino or heteroarylamino.
• L is a linker consisting of a chain of up to 20 carbon atoms, provided that up to three carbon atoms can be replaced with an oxygen, nitrogen or sulfur atom, and further provided that it can include substituents selected from a group consisting of: alkyl, alkenyl, alkynyl, aryl, heteroaryl, benzo, hydroxy, alkoxy, aryloxy, oxa, keto, amido, sulfonamido, or fluoro;
• R c and R d are independently selected from a group consisting of hydrogen, alkyl, alkenyl, alkynyl, alkoxy, aryl, heteroaryl, alkylamino, dialkylamino, arylamino or heteroarylamino.
• the provided compounds have the general structure Ar'-L'-L 2 -L 3 -Ar 3 wherein:
• Ar 1 and Ar 2 are aromatic rings independently selected from a group consisting of benzene, naphthalene, pyridine, pyrimidine, pyrazine, quinoline, isoquinoline, pyrrole, furan, thiophene, imidazole, pyrazole, oxazole, thiazole, isoxazole, indole, benzimidazole, benzothiazole, benzoxazole, provided that the aromatic ring may contain up to seven substituents selected from a group consisting of: hydrogen, alkyl, alkenyl, alkynyl, alkoxy, aryl, heteroaryl, amino, alkylamino, dialkylamino, arylamino, heteroarylamino, hydroxy, or halo. The substituents can also join together to form a ring of up to 12 atoms,
• L 2 is a linking group selected from a group consisting of a chain of up to
• the provided compounds have the general formula:
• L 2 is a linking group selected from a group consisting of a chain of up to 10 carbon atoms, provided that up to three atoms can be replaced with an oxygen, nitrogen or sulfur atom, and further provided that these atoms can contain substituents selected from a group consisting of: alkyl, alkenyl, alkynyl, aryl, heteroaryl, benzo, hydroxy, alkoxy, aryloxy, oxa, keto, amido, sulfonamido, or fluoro
• the provided compounds are selected from the following list of compounds (Fig. 2)
• This invention provides a novel strategy for identifying lead compounds that may act as subtype-specific HDAC inhibitor/modulators.
• the strategy consists of several iterative steps:
• Step 1 for a given HDAC complex of interest, the structure or substructure of the HDAC bound to its associated regulatory protein is solved or its structure or substructure that contains functionally important interfaces is obtained.
• Step 2 the structure is used for docking analysis of existing or new potential HDAC inhibitors that may bind the protein-protein interface. The virtual screen will be guided by functional data such as if the HDAC inhibitor showed effect in cellular processes involving the target HDAC complex and if the HDAC inhibitor seems to act through mechanisms other than active site inhibition.
• Step 3 the structure and related biochemical information is also used to guide the development of assays that can be used to screen compounds that can disrupt the intended protein-protein interface.
• Step 4 once such leads are found, their complexes with the protein target is characterized using the structural study system established in Stepl.
• Step 5 the structural information, in combination with relevant chemistry methodologies is used to guide the design of analogs that can bind the target protein with higher affinity and specificity. The methods used are similar to that of Step 2.
• Step 6 the designed analogs are synthesized and analyzed by assays established in Step 3. Finally, the optimized compounds are used for in vivo studies to test if they can mimic the effects of the parent compound but with higher potency and less non-specific/side effects.
• Class Ha HDACs play crucial roles in neuronal survival/synapse formation, T cell selection/activation, and muscle remodeling. Dysregulation of these activities are implicated in a number of diseases, including neurodegeneration, inflammation and cardiac hypertrophy. Some HDACi developed for cancer therapy showed beneficial effects against these disorders. Although the non-specific nature of these HDAC inhibitors prevent their clinical applications in these diseases, these observations raise an intriguing question whether the observed therapeutic effects were related to class Ha HDACs, and whether selected disruption of class Ha HDAC function could be a viable strategy for treating these diseases. To address these questions, small molecules that can specifically disrupt the function of class Ha HDACs are needed.
• the MEF2-binding molecules developed for treating various human diseases mentioned above could be administered orally, intramuscular, intraperitoneal, subcutaneous, intravenous injections. Other delivery methods are also possible, and the exact protocol will depend on the conditions that are being treated. The dose could also vary according to specific clinical applications. But the standard assays at which the compound shows effect in vitro is around 0.1 — 10 ⁇ M in vitro and 1-10 mg per KG of body mass in animal model studies.
• Preferred compounds provided under this invention shown in Figure 2 exhibited a wide range of affinity in binding to MEF2 in vitro and in vivo, and could serve as lead compounds to develop MEF2-based therapeutics in muscle, immune and nervous systems as mentioned above.
• the compounds indeed showed effect in promoting regulatory T cell functions in vitro and in mouse model, and are therefore potential drug leads for autoimmune diseases and preventing transplant rejection.
• the MEF2-binding molecule NKL30 at 0.15 ⁇ M greatly enhanced regulatory T cell function as evident by the enhanced suppression activity in vivo.
• the compound at 1 mg/KG body mass administered by intravenous injection also greatly enhanced the Treg function in vivo.
• class Ha HDACs are selectively expressed in muscle, brain and T cells, consistent with their functions in these tissues.
• the activity of class Ha HDACs is tightly regulated by the calcium signal, a predominant second messenger in tissues where class Ha
• HDACs are expressed.
• class II HDACs contain a large regulatory domain N-terminal to the catalytic domain, which confers unique properties to this subclass of HDACs.
• the N-terminal regulatory region contains domains and motifs that interact with a variety of proteins, including those regulating the calcium responsiveness of class II HDACs, such as CaM, CaMK and 14-3-
• class II HDACs targeting class II HDACs to specific promoters such as MEF2 and BCL-6, and other epigenetic regulators and effectors such as class I HDACs, CtBP and HP-I that function cooperatively with class Ha HDACs.
• epigenetic regulators and effectors such as class I HDACs, CtBP and HP-I that function cooperatively with class Ha HDACs.
• MEF2 is a family of sequence-specific transcription factors (MEF2A-D) that has the same expression pattern as class Ha HDACs and is also implicated in neurodegeneration, inflammation and cardiac diseases.
• the MEF2 family of transcription factors share a highly conserved N-terminal region, referred to as the MADS-box/MEF2S domain, that mediates DNA binding, dimerization and protein-protein interactions with a variety of transcription factors and co-regulators.
• Class Ha HDACs do not bind DNA but depend on interaction with MEF2 to target specific chromatin regions for deacetylation. Blocking this interaction is selected as a potential way to disrupt the function of class Ha HDACs.
• Example 4 Development of a sub-class specific HDAC inhibition assay [00104] A series of MEF2 -dependent luciferase reporter assays with transiently transfected MEF2D, HDAC4 and the co-activator p300 were used initially to screen various compounds. But these assays gave weak signal and high frequency of false positives, probably due to the complex transcription activation mechanisms of MEF2 and interference from endogenous factors. Through these observations, it was discovered that a highly sensitive and specific assay that can recapitulate the molecular interaction between HDAC4 and MEF2 inside cells is essential.
• the inventors devised a mammalian two-hybrid system that is capable of detecting the interaction between HDAC4 and MEF2D with minimal interference from endogenous factors (Fig. 3).
• Fig. 3 endogenous factors
• GAL4-MEF2D GAL4-MEF2D
• HDAC4-VP16 MEF2-binding motif of HDAC4 fused with VP- 16
• GAL4Luc GAL4-driven reporter plasmid
• Example 5 Identifying selective inhibitors of the MEF2/HDAC interaction [00107] To reduce the complexity of the screening, the vast amount of functional data on existing HDAC inhibitors was utilized. Although most of the these inhibitors target the catalytic domain, some of the compounds discovered through the cell based histone acetylation assays may affect other aspects of HDAC function, including the binding of class TIa HDACs to MEF2. With this in mind, we performed virtual screen (3D docking) against a small molecule database using a pharmacophore model derived from the crystal structure of the HDAC9:MEF2 complex. Although this search did not yield a novel target, it did show that the hydrophobic pocket of MEF2 prefers compounds with two aromatic rings connected by a linker of certain length.
• TSA trichostatin A
• the IC50 of PAOA on HDAC4:MEF2 interaction is around 5 ⁇ M based on the mammalian two-hybrid assay, similar to that determined using histone acetylation inhibition assay.
• the Kd for HDAC4 binding to MEF2 was previously determined to be 0.47 ⁇ M. If we assume the equilibrium concentration of HDAC4 is ⁇ 0.5 ⁇ M under our assay condition, the Kd for the binding of PAOA to MEF2 is estimated to be 5 ⁇ M. However, the estimated Kd could be larger if the free HDAC4 concentration is lower in the cell-based assay.
• HDAC4 at various concentrations generated a series of well-defined sensorgrams (data not shown). MEF2A incubated with increasing concentrations of PAOA showed dose dependent decrease of binding to the immobilized HDAC4 (Fig. 5). Analysis of the Biacore data indicates that the competitive binding reaction is complex, whereas direct binding of BML-2I0 to MEF2 was beyond the detection limit of the instrument. These technical limitations made it difficult to obtain a quantitative binding constant. Nevertheless, the preliminary data suggest that BML-210 indeed bind MEF2 competitively with HDAC4 in vitro.
• PAOA was originally discovered as part of a group of compounds that selectively induce acetylation of histone but not tubulin, presumably through inhibition of HDACs other than HDAC6, a tubulin-specific HDAC.
• PAOA binds MEF2 competitively with HDAC4 in vitro.
• the inserts on the right illustrate the assay by Biacore.
• HDAC4 red helix
• MEF2 green cross. deacetylase.
• HDAC6 which belongs to the class lib subfamily, does not have the MEF2 ⁇ binding motif conserved in class Ha and does seem to require MEF2 for function.
• PAOA and its derivatives have been recently shown to enhance the expression of frataxin in Friedreich's ataxia. Although the mechanism seems to involve induced histone acetylation, more potent but less specific HDAC inhibitors such as TSA and SAHA showed no effect on frataxin expression despite being able to induce higher level total histone acetylation in cells than PAOA. These observations suggest that PAOA and its derivatives possess a unique function to inhibit a specific HDAC or HDAC complex involved in frataxin silencing. Furthermore, the molecular basis for the action of PAOA can be further clarified with the crystal structure of BML- 210 bound to MEF2 disclosed in this invention.
• this structure also reveals for the first time a likely binding site for the ortho-aminoanilide moiety present in BML-210, as well as PAOA and in other benzamide-containing HDAC inhibitors. Notably, this binding site is different from the HDAC enzyme's active site as has been postulated previously for this class of HDAC inhibitors.
• Example 5 Preparation of complexes of BML-210 bound to MEF2 on DNA and the crystals of the BML-210:MEF2:DNA complex and the atomic details of the complex structure
• MEF2A1-78 was created by PCR amplification from MEF2AFL and cloning into the pET30b expression vector. Protein was expressed in E.
• Oligonucleotides (Santelli and Richmond, 2000) were purchased from IDT DNA technologies, purified using MonoQ FPLC column followed by dialysis, lyophylization and annealing using thermal cycler.
• 1/10 th protein sample volume of 1OmM BML 210 was added to the protein samples at Q.5mg/ml and concentrated to approximately 17mg/ml(0,9mM), and DNA duplex was added at 1 :1 ratio prior to setting trays (10%DMSO end concentration). Plate like crystals were obtained by hanging drop vapor diffusion conditions at 18C using 24% PEG4000, 14OmM NaCI, 5mM MgCl 2 , 1OmM CaCI 2 , 0.004%NaN 3j 3.3% glycerol, 5OmM TrisHCl (pH 5.8 - pH8.18). Crystals with drug density were obtained at pH 8.18.
• the structure is solved by molecular replacement using ITQE.pdb as search model (refs Richmond 2000).
• the final model has an Rfree of 26% and Rw of 23%.
• the coordinates are attached (1 l .l_001_nr_nh_bml.pdb).
• Class Ha HDAC can repress transcription independent of the deacetylase activity.
• a naturally occurring splicing variant of HDAC9 that lacks the entire C-terminal catalytic domain also known as MITR
• MITR is a potent transcription repressor of MEF2-dependent gene expression, presumably by recruiting other epigenetic effectors such as HPI and CtBP.
• small molecule inhibitors that target the catalytic domain of class Ha HDACs cannot eliminate the full epigenetic silencing potential of these proteins, which may explain the ineffectiveness of TSA and SAHA in reactivating frataxin expression.
• PAOA can block the recruitment of HDAC activity and other transcription repressors together.
• MEF2 is also involved in gene activation by recruiting transcription activators such as CBP/p300
• current data suggest that the main effect of PAOA on MEF2 dependent gene expression is alleviating the silencing effect of class Ha HDACs and other transcription repressors.
• BML-210 adopts an extended conformation to bind into the hydrophobic pocket of MEF2 (Pig. 1). This is also the binding site for the MEF2-binding motif conserved in class Ha HDACs and Cabin 1. Since one end of the electron density resembles a simple aromatic ring and is surrounded by a number of hydrophobic residues including Leu66, Leu67, Thr70, Leu66', Leu67' and Thr70' (prime sign denote residues from the other monomer), we assigned this density to the phenyl group. The carbonyl group at this end is also in position to engage in hydrogen bonding interactions with Thr70' (Fig. 1).
• MEF2-binding small molecules can be achieved using several known structures of MEF2.
• the small molecule Iigand whether naturally occurring peptide or synthetic molecule, binds to the deep groove on the surface of MEF2 dimer (Fig. 1).
• Fig. 2 A first series of potential inhibitors (Fig. 2) was synthesized, and already found that different compounds showed significantly different activity in their ability to inhibit the reporter signal in the mammalian two-hybrid assay. Most interestingly, one of these, compound 4, showed similar activity as PAOA but with no effect on the control signal driven by GAL-VP-16, suggesting that this new derivative is more specific than PAOA.
• Step 1 Pimelic acid (1 equiv) and 3-bromoaniline (1 equiv) were added to flask and stirred at 130 °C overnight.
• the reaction mixture was diluted in EtOAc and extracted with 10% potassium hydroxide.
• the aqueous layer was acidified to pH ⁇ 2 with cone. HCl and extracted with ethyl acetate.
• the organic layer was reduced under vacuum and recrystallized with acetonitrile/water.
• Step 2 To a solution of phenylenediamine in dichloromethane was added (Boc) 2 O (1 equiv) at rt and the mixture was stirred overnight. The reaction was concentrated under vacuum, diluted with ethyl acetate, and was extracted with three times with water and brine. The organic layer was reduced under vacuum and recrystallized chloroform/hexanes.
• Step 3 The product of Step 1 (100 mg) was dissolved in DMSO (3 mL) and to this solution was added Hunig's base (1 equiv), HBTU (1 equiv), and the monoprotected phenylenediamine product of Step 2. The resulting solution was stirred overnight at rt. The solution was diluted with ethyl acetate and extracted with three times with brine. The organic layer was reduced under vacuum and purified by column chromatography (hexanes/ethyl acetate gradient). The isolated product was dissolved in dichloromethane, cooled to °C and treated with trifluoroacetic acid (1 mL). The solution was allowed to warm to rt and stirred overnight.
• IPEX is caused by mutations of FOXP3. Nature genetics 27, 20-21.
• HDAC4 regulates neuronal survival in normal and diseased retinas. Science (New York, NY 323, 256-259.
• HDACs Histone deacetylases
• Histone deacetylase inhibitors reverse gene silencing in Friedreich's ataxia. Nature chemical biology 2, 551-558. Hori, S., Nomura, T., and Sakaguchi, S. (2003). Control of regulatory T cell development by the transcription factor Foxp3. Science (New York, NY 299, 1057-1061.
• FOXP3 is a homo- oligomer and a component of a supramolecular regulatory complex disabled in the human XLAAD/IPEX autoimmune disease.
• MEF2 a calcium-dependent regulator of cell division, differentiation and death. Trends Biochem Sci 27, 40-47.
• HDAC4 deacetylase associates with and represses the MEF2 transcription factor.
• Histone deacetylases focus on the nervous system. Cell MoI Life Sci 64, 2258-2269.
• Myocyte enhancer factor 2 mediates calcium-dependent transcription of the interleukin-2 gene in T lymphocytes: a calcium signaling module that is distinct from but collaborates with the nuclear factor of activated T cells (NFAT).
• NFAT nuclear factor of activated T cells
• HDAC inhibitors correct frataxin deficiency in a Friedreich ataxia mouse model.
• PIoS one 3, el 958. Santelli, E., and Richmond, TJ. (2000). Crystal structure of MEF2A core bound to
• HDAC8 provide insights into the class I histone deacetylases. Structure 12, 1325-1334.
• MEF-2 function is modified by a novel co-repressor, MITR.
• MITR novel co-repressor
• HDAC inhibitor Thomas, E.A., Coppola, G., Desplats, P,A., Tang, B., Soragni, E., Burnett, R., Gao, F., Fitzgerald, K.M., Borok, J.F., Herman, D., et al. (2008).
• the HDAC inhibitor
• FOXP3 controls regulatory T cell function through cooperation with NFAT. Cell 126, 375-387.
• FOXP3 is a novel transcriptional repressor for the breast cancer oncogene SKP2. J Clin Invest. Zuo, T., Wang, L., Morrison, C, Chang, X. s Zhang, H., Li, W., Liu, Y., Wang, Y., Liu,
• FOXP3 is an X-linked breast cancer suppressor gene and an important repressor of the HER-2/ErbB2 oncogene.

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